The principles of the silver complex diffusion transfer reversal process, hereinafter called DTR-process, have been described e.g. in U.S. Pat. No. 2,352,014 and the book "Photographic Silver Halide Diffusion Processes" by Andr e Rott and Edith Weyde--The Focal Press--London and New York, (1972).
According to the DTR process, a silver complex salt is image-wise transferred by diffusion from the image-wise exposed silver halide emulsion layer into the image receiving layer, where it is converted to a silver image usually in the presence of physical development nuclei. For this purpose, the image-wise exposed silver halide emulsion layer is developed in the presence of a developing agent and non-developed silver halide is converted by means of a silver halide complexing agent into a soluble silver complex salt while in contact with an image receiving layer.
A DTR-image bearing material an be used as a planographic printing plate wherein the DTR-silver image areas form the water-repellant ink-receptive areas on a water-receptive ink-repellant surface. The DTR-image can be formed in the image-receiving layer of a sheet or web material which is a separate element with respect to the photographic silver halide emulsion material (a so-called two-sheet DTR element) disclosed in e.g. DE-A-2.346.378 or in the image-receiving layer of a so-called single-support-element, also called mono-sheet element, which contains at least one photographic silver halide emulsion layer integral with an image-receiving layer in water permeable relationship therewith. It is the latter mono-sheet version which is preferred for the preparation of offset printing plates by the DTR method.
In order to prepare a lithographic printing plate from a monosheet DTR imaging element, the imaging element is developed in an alkaline processing liquid subsequent to an image-wise exposure. Preferably, the obtained plate is Subsequently stabilised using a stabilising liquid that reduces the surface pH of the plate after the alkaline development. An alkaline processing liquid generally comprises as active compounds, an inorganic alkali, a hydrophobizing agent, an inorganic sulphite and a silver halide solvent. Optionally, the alkaline processing liquid also comprises a developing agent. The stabilising liquid generally has a pH between 4 and 7, conveniently achieved with a buffer, and preferably also comprises a hydrophobizing agent.
A substantial waste of packaging, generally in plastic form, is generated by shipping the processing liquids in ready-to-use form thereby presenting an ecological disadvantage and causing inconvenience for customers using substantial volumes.
Accordingly, the need exists for bringing one or more processing liquids in a more concentrated and convenient form. In the past, proposals have been made to freeze dry or spray-dry a processing liquid so that it can be shipped in a solid form and dissolved in e.g. water when needed. However, Such procedure is not appropriate in case the processing liquid comprises an amine as a silver halide solvent because the latter is generally liquid at ambient temperature so that after freeze-dry or spray-dry a paste, which is inconvenient to handle, results.
JP 06-118575 discloses that an alkanolamine, also called aminoalcohol, may be solidified by adding a lewis acid such as HCl or H.sub.2 SO.sub.4 thereto. However, when an alkanolamine/HCl or an alkanolamine/H.sub.2 SO.sub.4 complex is dissolved together with the other active compounds of the processing liquid, a processing liquid is obtained that does not always yields printing plates with good performance, in particular not when processing under critical conditions such as fast processing or when the liquid has been in use for some time and becomes exhausted to some extend.